Northey Island is a remote tidal island in the Blackwater Estuary near Maldon, and the National Trust calls it the oldest recorded battlefield in Britain. Viking raiders used it as a base in AD 991 for the Battle of Maldon, fought by the causeway against Byrhtnoth, Ealdorman of Essex. Today it is a peaceful haven for Brent geese, redshank, curlew and plovers, and a pioneering site for managing coastal change, where sections of sea wall have been removed so that new saltmarsh can form. The Trust's 3.16-mile Northey Island circular walk starts at Promenade Park car park in Maldon. Dogs are welcome on a short lead of no more than 2 metres in spring and early summer and always near livestock, and under very close control at other times. The island is open to visitors for only part of the year, with no access to the house, gardens or saltmarsh. Reviewers praise the birdwatching and the bird hide. One tip from regular visitors: check Maldon tide times, as the causeway is covered for about three hours either side of high tide.